Raspberry Pi 4 Model B (4GB) with "pcie: link down" error

Support Raspberry Pi
1

Hi, has anyone come across a “link down” error in “dmesg”, on a Raspberry Pi 4 Model B?

I had it stored for a few months while I was using another R-Pi 4 Model B (8GB) and I simply swapped the SD card between them.
I realised that the USB wasn’t working and “lsusb” would return nothing.
After digging around and downloading a fresh Raspbian image with all the updates, I checked “dmesg” and it had the following error:

[    1.582992] brcm-pcie fd500000.pcie: link down

I checked “lspci”, and that too didn’t return anything, which made sense for the USB disappearance, since the USB controller is accessed through the pcie bus.

A few suggestions on Google pointed to update the bootloader and the VL805_FW for the USB controller, but that didn’t work.
The bootloader was successfully updated to the latest stable version, but when I tried to update the USB firmware, it simply wouldn’t boot at all, flashing the green LED 4 times slowly, followed by 5 times fast.

I removed the SD card, and I deleted the 3 files “recovery.bin”, “vl805_fw.bin”, “vl805_fw.sig” which were created just before the reboot, and it would reboot normally again.

If anyone has any other software fix to suggest, I’d appreciate it, since I’m running out of options, and I’m thinking that it’s probably a hardware issue.

The “i2cdetect” displays the Argon Fan HAT’s address (1A), which I can access, and set the fan’s speed using “i2cset -y 1 0x1A 0x64” for example for full blast or “i2cset -y 1 0x1A 0x00” to turn off the fan, so at least there’s still some life to it:

pi@raspberrypi:~ $ i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- 1a -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --

My next option would to try a few test points on board with an oscilloscope, but I wouldn’t know where to look first.

Does anyone have anything to suggest?

2

Hi Sofoklis,

If you’ve tried USB firmware and a fresh OS install, I don’t think there’s much you can try. From what I’m reading errors like that generally occur from incorrect PCIe wiring, and that can’t be an issue on a regular old Pi.

When/where did you buy the Pi? a few months is usually within warranty depending on the place.

3

@James I bought it on May 2020, so it’s out of warranty anyway. I tried all the test points, and all the expected voltages were there. The outputs of the crystal oscillators were also looking ok. There’s no visible short or damage on the board, so it may be a BGA chip that needs to be reflowed, which is out of my capabilities.
Thanks for your response

1 Like
4

Hi, I am experiencing the sam problem and came across this thread. Did you eventually find a software based solution or is it an unfixable hardware issue? Thank you.

5

Hi, unfortunately I haven’t found a software solution to that issue. I have two Pi 4 so, I’m using the second one at the moment, and I kind of gave up trying to salvage the other one…
If I find the time to deal with it again, and have any progress, I’ll definitely post it here though.

1 Like